Nanoparticle Interactions and Nanoscale Transport in Polyelectrolyte Brushes
Nanoparticles come in a variety of sizes, shapes, chemistries, and functionalities, ranging from folded proteins, viruses, and quantum dots.
Bound Layer Exchange in Polymer Nanocomposite Melts
Fuel cells are an increasingly important technology for energy conversion, particularly for transportation. Perfluorosulfonic acid (PFSA) polymers have been used for decades as proton exchange membranes (PEMs) within hydrogen fuel cells, because they have excellent proton transport properties along with high chemical stability.
Nanoparticle Interactions and Nanoscale Transport in Polyelectrolyte Brushes
Karen I. Winey and Russell J. Composto
Nanoparticles come in a variety of sizes, shapes, chemistries, and functionalities, ranging from folded proteins, viruses, and quantum dots. Because nanoparticles at interfaces underpin a broad and expanding range of applications including nanoscale filtering and detection, this project will research the motion of individual nanoparticles in complex local environments. Most previous studies of nanoparticle motion have been limited to studies of ensembles of particles or particles in homogeneous environments, and these studies provide a valuable foundation upon which to build. Recent advances in imaging methods and data processing methods enable the study of nanoparticles in heterogeneous environments one particle at a time. Interferometric scattering microscopy provides exceptional spatial and temporal resolution and was originally developed to image biomolecules at interfaces. This project will use this advanced method to study nanoparticle motion at interfaces, particularly interfaces with various functionalities, and under applied electric fields. These studies and fundamental understanding will inform advanced strategies for separating natural or synthetic nanoparticles based on size, shape, or charge by designing interfaces that selectively trap nanoparticles. This new understanding will also provide strategies for producing higher quality nanoparticle products with more uniform characteristics. Differentiating mechanisms of nanoparticle dynamics can also lead to advanced sensing applications.
Winey and Composto will mentor undergraduate researchers, engage with public outreach events across Philadelphia, and partner with a program to bring the science laboratory to underserved high school students.
Bound Layer Exchange in Polymer Nanocomposite Melts
Karen I. Winey
Robert A. Riggleman
Polymer nanocomposites (PNCs) are an emerging class of materials in a variety of applications including structural materials for infrastructure and membranes for separations. Preventing aggregation of nanoparticles in PNCs frequently requires systems with strong attractions between the polymer and the particles, leading to polymer adsorption to the particle surfaces. This bound layer of polymer on the nanoparticlesexhibits different properties that polymers in the absence of nanoparticles. Overall, properties of the bound polymer layer is critical to the properties and performance of PNCs. For example, bound polymer layers in PNCs can promote uniform nanoparticle dispersion, improve mechanical properties, and tune transport properties. Despite the importance of the bound layer to PNC fabrication and performance, the time-dependentproperties of bound polymers remain largely unknown, especially at the chain-scale. To optimize PNCs properties and effectively design PNCs for advanced applications, additional fundamental studies are necessary to understand and manipulate the bound polymer layer. Meaningful progress requires a multi-pronged effort that combines experiments and simulations to systematically probe the evolution of the bound layer structure and the exchange between bound and unbound polymers in PNCs.
The goal of our collaborative proposed work is to develop and demonstrate a small-angle neutron scattering (SANS) technique to directly probe chain-scale exchange of bound polymers in the matrix (unbound) polymers in PNCs. We will combine this technique with molecular dynamics (MD) simulations to study the effect of annealing temperature and time on the bound polymer layer exchange and to demonstrate control of this exchange by altering the NP-polymer interactions. Achieving these goals will broadly impact the field of polymer science and engineering. Beyond new insights about the chain-scale exchange and properties of bound polymer layers in PNCs, our SANS method can be readily applied to a variety of PNC systems and colloidal solutions. Furthermore, the unique samples fabricated in this study can be used to study the bound or free polymers by various other techniques (e.g. neutron spin echo, NMR).
Selected Recent Publications: